1. Field of the Invention
The present invention relates to an electron emission device and a method of manufacturing the same. More particularly, the present invention relates to an electron emission device having improved electron emission efficiency, extended lifetime, and improved electron emission uniformity, and a method of manufacturing the same.
2. Description of the Related Art
In general, electron emission devices may use a thermionic cathode or a cold cathode as an electron emission source. The types of electron emission devices that use cold cathodes may include field emission (FED) devices, surface conduction emitter (SCE) devices, metal-insulator-metal (MIM) devices, metal-insulator-semiconductor (MIS) devices, and ballistic electron surface emitting (BSE) devices.
FED devices use the principle that electrons may be readily emitted due to a field emission difference in a vacuum when a material having a low work function or a high β function is used as an electron emission source. FED devices employ electron emission sources formed of a material utilizing, e.g., molybdenum, silicon, etc., as the main material having a sharp tip, a carbon material, e.g., graphite, diamond like carbon (DLC), etc., or a nano material, e.g., nano tubes, nano wires, etc.
SCE devices use the principle that electrons may be emitted from fine cracks, which are electron emission sources, when a current flows through a surface of the conductive thin film by applying a voltage to the first and second electrodes. SCE devices employ electron emission sources in which fine cracks may be formed on a conductive thin film after the conductive thin film is formed between first and second electrodes facing each other on a substrate.
MIM and MIS devices employ electron emission sources respectively having MIM and MIS structures, where electrons may be emitted and accelerated toward a metal having a low electron potential from a metal or a semiconductor having a high electron potential when a voltage is applied between both metals or a metal and a semiconductor which are located interposing a dielectric layer.
BSE devices use electrons that are not dispersed, but run straight in a direction when the size of a semiconductor is reduced to a dimension less than a mean free path distance of electrons in the semiconductor. BSE devices employ an electron emission source that may emit electrons when a voltage is applied to an ohmic electrode and a metal thin film after an electron supplying layer made from a metal or a semiconductor is formed on the ohmic electrode, and an insulating layer and the metal thin film are formed on the electron supplying layer.
FIG. 1 illustrates a partial exploded perspective view of a double FED type electron emission device, FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1, and FIG. 3 is an enlarged view of portion III of FIG. 2.
Referring to FIGS. 1 through 3, an electron emission device 101 may include a first substrate 110, cathodes 120, gate electrodes 140, a first insulating layer 130, and electron emission sources 150. The electron emission device 101 may face a front panel 102 spaced apart with spacers 60.
The first substrate 110 may be a board having a predetermined thickness. The cathodes 120 may extend in a direction on the first substrate 110. The gate electrodes 140 may cross the cathodes 120. The first insulating layer 130 may be interposed between the gate electrodes 140 and the cathode 120 in order to insulate the cathodes 120 from the gate electrodes 140. Electron emission source holes 131 may be found in the first insulating layer 130.
The electron emission sources 150 may be electrically connected to the cathode 120. The electron emission sources may be formed of, e.g., a carbon material, a nano material, etc.
The electron emission device 101 may be used as an electron emission display device 100 forming a display cell 103 which generates visible light to realize images. In order to be used as a display device, a phosphor layer 70 may be further included on a front surface of the electron emission device 101. The phosphor layer 70 may be installed together with an anode 80 which accelerates electrons towards the phosphor layer 70. A front substrate 90 may support the anode 80 and the phosphor layer 70.
In the electron emission display device 100 having the above structure, the electron emission sources 150 that include an electron emission material, e.g., a carbon material, a nano material, etc., may be manufactured by using a direct growing method, e.g., a printing method, a chemical vapor deposition (CVD) method, etc. However, when the electron emission material is grown using the above methods, the electron emission material forming the electron emission sources 150 may in many cases not be exposed on a surface of the electron emission sources 150, but may be buried in the electron emission sources 150. Also, even if the electron emission material is exposed on the surface of the electron emission source, the electron emission material may be agglomerated or grown in lateral directions.
If the electron emission material is not exposed to the outside, a smooth emission of electrons by a tip discharge effect may not be reached. Even when the electron emission material is exposed to the outside and agglomerated, electron emission efficiency may be reduced due to a screen effect. In this case, the screen effect may denote that when the electron emission material is agglomerated, the agglomerated electron emission material may perform as one electron emission material. Also, when the electron emission material is not agglomerated, but grown in lateral directions, considering that electrons must be emitted straight forward, there may be a high possibility of non-uniform emission of electrons.
Accordingly, there is a need to improve the problem of reduced brightness due to a non-uniform electron emission or reduced electron emission characteristics.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.